BudgetWhat you have assigned to this ad account out of your balance. An account cannot spend more than its budget.
SpentWhat the account has spent so far, updated every 30 minutes.
Balance leftBudget minus spent. This is what the account can still spend.
Available to allocateMoney in your balance not yet assigned to any account. Shown on Overview.
Moving budgetYou can add budget from your available balance, or move unspent budget from one account to another. Money already spent cannot be moved.